Durability performance of RC beams strengthened with CFRP laminates and galvanized steel mesh bonded with epoxy and mortar systems

The galvanized steel mesh (GSM) systems are novel strengthening materials for the concrete structural elements, but their mechanical and long-term durability properties are needed to be investigated to enhance understanding and reliability in their use. This study investigates the behavior of reinforced concrete (RC) beams strengthened with carbon fiber reinforced polymers (CFRP) and GSM sheets under harsh climatic conditions of saline water and direct sunlight. The main focus was to recommend two important reduction factors, the bond reduction factor and the overall flexural reduction actor, when concrete beams are subjected to two said environments for a long period. These factors were compared to the ones recommended by different codes. The CFRP sheets were attached to the beams' soffit with epoxy adhesive, whereas the GSM sheets were bonded either with epoxy (SME) or epoxy-based mortar (SMM). The specimens were weathered under saline water and direct sunlight for a period of 6, 12, and 24 months. The load-carrying capacity of CFRP, SMM, and SME strengthened specimens increased by 47%, 55%, and 55%, respectively, when compared to the unstrengthened specimens at 28 days. The bond capacity reduction factors (Rb) for CFRP, SMM, and SME strengthening systems were 0.75, 0.85, and 0.95 for saline water exposure, and 0.95, 0.85, and 0.85 for sun exposure, respectively, over a period of two years. On the other hand, the recommended overall flexure strength reduction factors (Rn) for CFRP, SMM, and SME strengthening systems were 0.85, 0.85, and 0.90 for saline water exposure, and 0.95, 0.90, and 0.90 for sun exposure, respectively. The results suggest that epoxy-based strengthening systems are more durable compared to the mortar-based systems under harsh climatic conditions.